Submitted to: Proceedings of the National Academy of Sciences
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/19/2006
Publication Date: 10/26/2006
Citation: Hyten, D.L., Song, Q., Zhu, Y., Choi, I., Nelson, R.L., Costa, J., Specht, J.E., Shoemaker, R.C., Cregan, P.B. 2006. Impacts of genetic bottlenecks on soybean genome diversity. Proceedings of the National Academy of Sciences. 103:16666-16671. Interpretive Summary: Maintaining a stable food source through crop improvement and reducing crop vulnerability to a new disease requires an understanding of how much of the genetic diversity of crop ancestors has been retained in modern crop cultivars. We determined the DNA sequence of 102 genes in each of 120 soybeans from four populations that represent the wild ancestor of soybean as well as ancient soybeans and soybeans that are currently grown. We find that current soybeans still retain half of the diversity that is present in its wild ancestor. In addition, we found that the wild ancestor has a large reservoir of rare and unique forms of genes that are not present in currently grown cultivars. However, because genes for disease resistance are very rare, generally occurring in less than 1% of ancient soybeans, the random incorporation of genes from unimproved crop ancestors is not an efficient approach to increase genetic diversity to combat vulnerability to disease as has been assumed. Instead, searches for specific genes or rare genes that control disease resistance will help to more effectively combat new soybean diseases. This information will be used by crop breeders and seed companies to increase the efficiency of searching for and incorporating genes from ancient species for purposes of crop improvement.
Technical Abstract: Maintaining a stable food source requires an understanding of how much of the genetic diversity in wild progenitors has been retained in modern crop cultivars. We sequenced 111 fragments from genes in four soybean populations that have undergone several genetic bottlenecks. We show that modern soybean does have low sequence diversity, but this is due to low diversity in the wild species, which was halved in the domestication bottleneck, but thereafter was not appreciably reduced by a limited number of founders, or by fifty years of intensive artificial selection. These data indicate that broad introgression of the wild species and landraces into the elite germplasm pool will not reduce the genetic vulnerability of modern soybean as has been generally assumed.